A motor vehicle fuel pump described in U.S. patent application Ser. No. 08/391,856, filed 22 Feb. 1995 (now U.S. Pat. No. 5,509,778) and assigned to the assignee of this invention, includes an electric motor, a high pressure pump, and a low pressure regenerative turbine pump ahead of the high pressure pump. The low pressure pump includes an annular pump channel, an impeller having peripheral vanes in the pump channel, a pair of radial vapor ports at an inside diameter of the pump channel on opposite sides of the impeller, and a pair of sidewall steps in the pump channel extending between an outside diameter and an inside diameter of the pump channel from ahead of the vapor ports to downstream sides thereof. The sidewall steps promote vapor separation by smoothly guiding liquid fuel with entrained vapor to the radial vapor ports.
U.S. Pat. No. 5,129,796, issued 14 Jun. 1992 and assigned to the assignee of this invention, describes a motor vehicle fuel pump including an electric motor, a high pressure pump, and a low pressure pump in which two separate regenerative turbine pumping stages are derived from vanes on opposite sides of a single impeller in a pump channel around the periphery of the impeller. The first pumping stage transfers fuel from a fuel tank into a reservoir in which the fuel pump is mounted. The second pumping stage transfers fuel from the reservoir to the high pressure pump. Liquid fuel with entrained vapor is expelled radially inward from the second pumping stage through clearance between a side of the impeller and an adjacent side of the housing in which the pump channel is formed.